Raman gain

Raman gain coefficient, whose maximum occurs at exact resonance, - oig = For a Lorentzian lineshape, the maximum gain coefficient is given by... 

Kroon R., Baggen M., Lagendijk A. Vibrational dephasing in liquid nitrogen at high densities studied with time-resolved stimulated Raman gain spectroscopy, J. Chem. Phys. 91, 74-8 (1989). 

I. Is it possible to observe a shift in coherent Raman scattering in the three-level system with A-type coupling We have done an experiment to obtain a femtosecond Raman gain spectrum in polydiacetylenes. The Raman spectrum is shifted to the red under increased pump (to i) intensity. By changing o>2> the amplification peak signal is to be shifted to lower frequency. If the optical Stark effect is observed, then, in principle, it should be possible to observe the effect of a high field on the coherent Raman spectrum (see Fig. 1). 

Raman gain Possible Developmental alternative to CARS... 

This Raman gain is interesting, since it extends the tuning range of optically pumped lasers, provided the pump laser itself is tunable and powerful enough. 

Further experiments are underway with this set-up, in order to study the Raman gain lineshapes and their saturation behavior, and to compare these results with a theoretical model. 

Figure 3.6-4 Schematic diagram for a few techniques in nonlinear (coherent) Raman spectroscopy (CSRS Coherent Stokes Raman Spectroscopy SRGS Stimulated Raman Gain Spectroscopy IRS Inverse Raman Spectroscopy (= SRLS Stimulated Raman Loss Spectroscopy) CARS Coherent anti-Stokes Raman Spectroscopy PARS Photoacoustic Raman Spectroscopy).

Stimulated Raman gain and inverse Raman spectroscopy (SRGS, IRS)... 

The methods of nonlinear Raman spectroscopy, i. e. spontaneous hyper Raman scattering (based on the hyperpolarizability) and coherent nonlinear Raman scattering (based on the third-order-nonlinear susceptibilities) are discussed in detail in Sec. 3.6.1. In Sec. 3.6.2 the instrumentation needed for these types of nonlinear spectroscopy is described. In this section we present some selected, typical examples of hyper Raman scattering (Sec. 6.1.4.1), coherent anti-Stokes Raman. scattering (Sec. 6.1.4.2), stimulated Raman gain and inverse Raman spectroscopy (Sec. 6.1.4.3), photoacoustic Raman spectroscopy (Sec. 6.1.4.4) and ionization detected stimulated Raman spectroscopy (Sec. 6.1.4.5). 

The advantages of the two coherent Raman techniques, stimulated Raman gain (SRGS) and inverse Raman spectroscopy (IRS), have been described in detail in Secs. 3.6.1.3 and 3.6.2.3. Here, we present an instructive example for each technique emphasizing the high resolution capability of the.se methods. 

Figure 6.1-25 High resolution multi-pass stimulated Raman gain spectrum (SRGS) of the Q-branch of the lower component of the Fermi resonance diad of C 02 at a pres.sure of 200 Pa (1.5 Torr) (Saint-Loup et al., 1990).

Coherent Raman spectroscopy Coherent Raman spectroscopy is a term that refers to a series of closely related nonlinear Raman techniques in which the scattered Raman radiation emerges from the sample as a coherent beam -coherent meaning that the photons are all in phase with one another. The coherent techniques include Stimulated Raman Scattering (SRS), Coherent anti-Stokes Raman Spectroscopy (CARS), Coharent Stokes Raman Spectroscopy (CSRS), and Stimulated Raman Gain Spectroscopy (SRGS). Although most of the nonlinear Raman techniques are also coherent techniques, there is one incoherent nonlinear Raman process called Hyper Raman. 

---